Process control systems, like those used in chemical, petroleum or other processes, typically include one or more process controllers communicatively coupled to at least one host or operator workstation and to one or more field devices via analog, digital or combined analog/digital buses or lines. The field devices, which may be, for example valves, valve positioners, switches, and transmitters (e.g., temperature, pressure, and flow rate sensors), perform functions within the process plant such as opening or closing valves and measuring process parameters. The process controllers receive signals indicative of process measurements made by the field devices and/or other information pertaining to the field devices, use this information to implement control routines and then generate control signals which are sent over the buses or lines to the field devices to control the operation of the process. Information from the field devices and the controllers is typically made available to one or more applications executed by the operator workstation to enable an operator to perform any desired function with respect to the process, such as configuring the process, viewing the current state of the process, modifying the operation of the process, etc.
Additionally, in many processes, a separate safety system is provided to detect significant safety-related problems within the process plant and to automatically close valves, remove power from devices, switch flows within the plant, etc., when a problem occurs which might result in or lead to a serious hazard in the plant, such as a spill of toxic chemicals, an explosion, etc. These safety systems typically have one or more separate controllers apart from the standard process control controllers, called logic solvers, which are connected to safety field devices via separate buses or communication lines installed within the process plant. The logic solvers use the safety field devices to detect process conditions associated with significant events, such as the position of certain safety switches or shutdown valves, overflows or underflows in the process, the operation of important power generation or control devices, the operation of fault detection devices, etc. to thereby detect “events” within the process plant. When an event (typically called a “cause”) is detected, the safety controller takes some action (typically called an “effect”) to limit the detrimental nature of the event, such as closing valves, turning devices off, removing power from sections of the plant, etc. Generally, these actions or effects include switching safety devices into a tripped or “safe” mode of operation which is designed to prevent a serious or hazardous condition within the process plant.
Systems within a process plant, such as process control systems and safety systems, typically may keep track statuses of various processes and/or the systems themselves. Input signals to a system may cause the status tracked by the system to change, and output signals generated by the system may depend on the current status of the system in addition to input signals to the system. U.S. Pat. No. 7,730,415, which is hereby incorporated by reference herein in its entirety for all purposes, details a control system within a process plant that uses state machine function blocks that are integrated into a function block diagram programming environment. In particular, such a state machine function block includes one or more inputs which are used to cause a state machine implemented by the state machine function block to change states. Further, the state machine function block determines a next state to which it is to transition based on state transition configuration data indicative of the next state. The state transition configuration data is retrieved from a database based on the current state of the state machine and at least one of the inputs. The state machine function block also includes one or more outputs that are generated based on the state of the state machine. The inputs of the state machine function block are associated with, for example, a process control system or a safety system, and the outputs may be used, for example, for control of field devices in the process control system or the safety system.
However, current process control systems do not have the ability to automatically execute various actions or functions associated with a transition out of a current state or a transition into a next state. Instead, users and administrators of current process control systems must manually execute or implement the actions or functions during state transitions. Therefore, the current process control systems are limited in their ability to carry out certain safety measures, control techniques, and other features associated with state transitions.